Get simple automotive 12 volt 30 amp relay and power it by a 120 volt AC input/12volt DC output transformer... I have picked up many a 1000/1200ma (1amp) out put 12 volt transformer at resale shops or garage sale or junk bins....
Dale
eggsalad wrote:Let me try another tactic...
If you got a 120/120 relay (that is, a relay triggered by 120v and the outputs are rated at 120v) well, 120 volts is a lot more than 12 volts. The output is just a switch. If the switch contacts are rated to 120v, surely they'll handle 12v just fine.
eggsalad wrote:Let me try another tactic...
If you got a 120/120 relay (that is, a relay triggered by 120v and the outputs are rated at 120v) well, 120 volts is a lot more than 12 volts. The output is just a switch. If the switch contacts are rated to 120v, surely they'll handle 12v just fine.
H.A. wrote:kludge wrote:You don't need a 120VAC trigger.
Any old 12VDC coil relay will work.
Put the coil on the output of the Converter but before the contacts of the relay.
The Converter will turn on when AC is applied and give you 12V on the output. The output from the Converter will power the relay coil, the contacts will close connecting the battery, and the battery will charge.
Let me know if you need a picture.
A picture might be nice,
As I envision by your description, What happens when 120vac is removed from the charger ?
Will the battery back feed thru the closed contacts to keep the relay coil energised ?
Further, Many of these 'smart chargers' wont switch on its charging output until it first measures a correct polarity voltage from the battery.
Its a safety feature what prevents its output from becoming energised if for example its output leads are shorted to each other or connected in reverse polarity.
I expect the small constant battery drain previously mentioned is related to this voltage measuring circuit.
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